Bad catalytic converter?

[smokin240]

Ive been having this problem for almost a year now. So far I have checked the MAFS, Coil, Plugs, Rotor, Intake, Fuel Filter, and for vacuum leaks. I've also had 5 mechanics, some of whom are friends look at it and one actually hooked it up to a computer to run codes on it. And still no luck. My car has about 168,000k on it and compression is anywhere from 135psi-145. So its pretty good for the mileage. Anyway, heres the problem... When I haven't drivin it for say atleast 8 hours it runs fine until it warms up. When that happens (engine temp is fine) the car lags out at low RPM when I push the pedal less than 1/4 the way or over half way down; so just before pushing the pedal half way down is when its pretty smooth in acceleration. It loses ALOT of power and acts almost like its being choked like its not getting enough air because it has a solid line of power 2500rpm-3000rpm and in higher rpm it chokes out again. Someone I work with said his Mercedes had the same symptoms, so he changed his cat conv. and it ran perfect. He says it was clogged, and it does that usaully rom high mileage cars. Ive been trying to fix this forever now and ran out of ideas until this. Could this actually be it? I need to take off my rusted heat shield before I can even look at it. Should it be glowing orange or really hot if its bad? Should I look for anything? Thanks all

[Camel]

if it is an s13, get an s14 hollow lower cat and use that for a couple of days. if it fixes it, just get a random tech cat to replace the original.

[nnkfws333]

I bad cat will smell like rotten eggs. You can just get anyone out of a junkyard and see what happens. Are you running cheap gas? Have you tried to replace your knock sensor or anything else?

[574-240sx]

If its glowing cherry red at night it is bad. Also the rotten egg smell will tell you its bad, but that doesn't happen all the time. Your catalytic converter is located right under the drivers seat right by the frame rail. Just look under the car and if if its glowing you can tell. You might have a hard time replacing it if it rusted pretty bad. If you do it yourself just get a highflow one.

[Prelude Guy]

I have a similar problem with my 89 240SX SE hatch. The car will rev fine if I push the gas pedal down 15% of the way down. However, the car bogs BAD if I push the gas pedal down more than that.

When I do push the gas pedal down, I can hear the intake sucking in air, but the motor just doesn't want to go.

Let me know if the cat cures your problem.

I changed the dist. cap, rotor, fuel filter, checked for vaccuum leaks, ground wire, fuel pump, plugs, wires, and the O2 sensor.Still, the problem exists.

My exhaust system is fine...and the downpipe is welded to the cat...which is welded to the cat-back. The exhasut system was changed only 2 years ago. However, I am not sure if the cat was changed. I don't think it was.

I eventually plan to upgrade the motor to an SR20DET. Should I buy a 3" high flow cat now?? Can I take the car to a shop to have them test my cat??

[smokin240]

It does smell sometimes pretty bad, but I think it may be my clutch going out. But yeah I was also told by someone that they hear knocking from my engine as well. funny thing is the one that noticed it isnt a mechanic but the 5 others are and never noticed it. And personally I dont really hear it but I guess I could be wrong. I was already thinking about getting a high flow cat from ebay, its about 60 but the one I have on now is so rusted im going to have to grind the bolts off. next chance i get ill check to see if its glowing at all. Ill let you know if its it but I dont think I will find out for a few weeks if thats really it. thanks

by the way, sometimes i use 93 octane and if gas is way expensive ill use 87, i never use the middle i dont know why :-/ Ive only had the car for 8k miles anyway, the other person had it for the other 160k and im not sure what he used.

[johna_99_99]

i have the exact same problem....my car also seems to be lacking power and im not sure whats going on....let me know if the problem stops agfter intalling that new cat....

[onosqv]

It does smell sometimes pretty bad, but I think it may be my clutch going out. But yeah I was also told by someone that they hear knocking from my engine as well. funny thing is the one that noticed it isnt a mechanic but the 5 others are and never noticed it. And personally I dont really hear it but I guess I could be wrong. I was already thinking about getting a high flow cat from ebay, its about 60 but the one I have on now is so rusted im going to have to grind the bolts off. next chance i get ill check to see if its glowing at all. Ill let you know if its it but I dont think I will find out for a few weeks if thats really it. thanks

by the way, sometimes i use 93 octane and if gas is way expensive ill use 87, i never use the middle i dont know why :-/ Ive only had the car for 8k miles anyway, the other person had it for the other 160k and im not sure what he used.

I luv ebay, but be careful of some of the "hi flow" they advertise. Most of them are just test pipes. The only ones I know of that are truly hi flow on ebay are the "universal" ones that you have to get flanges for and weld yourself. Those are the random tech or carsound or magnaflow ones (those are the good ones).

You can also get a hi-flow from AZHitman prewelded w/ a spinning flange (I got mine from him - works awesome).

[flatblacksr]

I also have a similar problem but my car revs just fine. when i give it like 20% throttle ill accelerate decent but if i floor it while im drivin the car will bog down really hard and accelerate slower than when i was givin it 20% throttle. Also my turbo sounds like if its workin way harder than it should be. when i check my boost it reads between 7 and 8 psi consistently. if u ever figure out your problem lemme know.

[InsanityInc]

If your compression is 135-145, your engine is pretty much dead. Stock is 179, minimum is 155. (I'm assuming you have a KA)

[fatboy]

hook up a vacuum gauge on the intake. rev it up and keep the engine speed up. if the vacuum drops off, then there is restriction in the exhaust